But your argument with Alexa is in my view in the wrong "direction." Alexa doesn't know what it means to be a light, and perhaps a computer "never" will.

But the real question is, how do humans "know what a light is", or what do you mean when you say a human knows what a light is.

My intuition is similar to yours, that our living in a "deep and complex" environment has something to do with it, but what?

The deep and complex environment might explain how we learn what a light is, but what is it? To put in Fodor's terms, what is the representation?

When you or I "think" (what is thinking?) of the light (what does it mean to think of the light?), what is going on in our heads?

I suspect whatever theory of representation you come up with will look something like a computational theory. The notion or concept of the light will be "stored" and have "relationships" and so forth.

edit: readability